The present invention relates to breathable absorbent articles like baby diapers, adult incontinence articles and in particular to sanitary napkins or pantiliners. According to the present invention the articles are provided with an apertured backsheet for breathability. At least one of the breathable layers of the backsheet comprises a resilient, three dimensional web which consists of a liquid impervious polymeric film having apertures. The apertures form capillaries which are designed such that the backsheet provides an increased barrier to liquid passage out of the article and maintains water vapour permeability when the web is exposed to compressive pressure.
The primary consumer needs which underlie development in the absorbent article field, in particular sanitary napkins, catamenials, or pantiliners is the provision of products providing both a high protection and comfort level.
One means for providing consumer comfort benefits in absorbent articles is by the provision of breathable products. Breathability has typically concentrated on the incorporation of so called xe2x80x98breathable backsheetsxe2x80x99 in the absorbent articles. Commonly utilised breathable backsheets are microporous films and apertured formed films having directional fluid transfer as disclosed in for example U.S. Pat. No. 4,591,523. Both these types of breathable backsheets are vapour permeable allowing gaseous exchange with the environment. This thereby allows for the evaporation of a portion of the fluid stored in the core and increases the circulation of air within the absorbent article. The latter is particularly beneficial as it reduces the sticky feeling experienced by many wearers during use, commonly associated with the presence of an apertured formed film or film like topsheet.
A drawback associated with the use of breathable backsheets in absorbent articles is the negative effect on the protection level performance by leakage, known as wet through, onto the users garment. Although, breathable backsheets in principle only allow the transfer of materials in the gaseous state, physical mechanisms such as extrusion, diffusion and capillary action may still occur and result in the transfer of the fluids from the absorbent core through the backsheet and onto the users garments. In particular, these mechanisms become more dominant if the backsheet is compressed e.g. during physical exertion, especially for heavy discharge loads or over extended periods of time. Thus, whilst the incorporation of breathable backsheets in absorbent articles is highly desirable from a comfort standpoint, since the primary role of a backsheet still remains the prevention of liquid leakage, conventional breathable backsheets have not always been satisfactorily incorporated into products.
The problem of wet through onto users garments due to the incorporation of such breathable backsheets in absorbent articles has indeed also been recognized in the art. Attempts to solve the problem have mainly resided in the use of multiple layer backsheets such as those illustrated in U.S. Pat. No. 431,216. Similarly European patent application no. 710 471 discloses a breathable backsheet comprising an outer layer of a gas permeable, hydrophobic, polymeric fibrous fabric and an inner layer comprising an apertured formed film having directional fluid transport. The backsheet construction preferably has no liquid transport/wet through under certain specified test conditions. Also European patent application no. 710 472 discloses a breathable backsheet consisting of at least two breathable layers which are unattached to one another over the core area. The backsheet construction preferably has no liquid transport/wet through under certain specified test conditions.
U.S. Pat. No. 4,713,068 discloses a breathable clothlike barrier for use as an outer cover for absorbent articles. The barrier comprises at least 2 layers, a first layer having a specified basis weight, fiber diameter and pore size and a second layer comprising a continuous film of poly(vinyl alcohol) having a specified thickness. The barrier also has a specified water vapour transmission rate and level of impermeability.
However, none of the above proposed solutions have been able to provide a fully satisfactory solution to the problem of wet through prevention under all conditions, especially when the article incl. the breathable backsheet is compressed.
U.S. Pat. No. 5,591,510 as well as WO 97/03118 and WO 97/03795 disclose an apertured film layer having capillaries which are disposed at an angle relative to the plane of the film, which films are referred to as slanted capillary films. This film structure is provided as a improvement for incorporation into clothing and garments which are breathable, yet non transmitting liquids toward the wearer of such garments. Also the use of such slanted capillary films is indicated in the context of absorbent articles but as a topsheet, particularly in FIG. 16 of U.S. Pat. No. 5,591,510 the combination of such slanted capillary films together with an absorbent material is disclosed, however not in the context of disposable absorbent articles according to the present invention.
Another problem which occurs when the article is put to use and exposed to compressive pressure or high discharge loadings is that the effective breathability is drastically reduced. For example when liquid has contacted a microporous film the water vapour transmission is effectively eliminated. When considering apertured capillary films of the prior art the water vapour transport is also drastically reduced when they are exposed to pressure but remains at a low level.
It is hence an objective of the present invention to provide absorbent articles which have a breathable backsheet designed such that they provide an increased barrier to liquid passage when exposed to pressure while at the same time the water vapour permeability, i.e. what is conventionally understood as breathability, is less reduced than the water vapour permeability of conventional apertured capillary films (provided they are not made from a water vapour permeable material).
It is another objective of the present invention to provide a disposable absorbent article having and maintaining improved breathability while having and maintaining an acceptable level of protection, i.e. being exceptionally leakage resistant, in particular when the article is exposed to pressure.
The present invention relates to breathable disposable absorbent articles of a layered construction such as baby diapers, adult incontinence articles and in particular sanitary napkins or panty liners. Also articles such as underarm sweat pads, breast pads, or shirt scholars may benefit from the present invention. Typically such articles are of layered construction with each layer or group of layers having a garment facing surface which is oriented to face in the direction of a garment during use of the article and a wearer facing surface facing in the opposite direction. Typically such articles comprise a liquid pervious topsheet forming the wearer facing surface of the article, an absorbent core and a breathable backsheet forming the garment facing surface of the article. The absorbent core is interposed between the topsheet and the backsheet. However, according to the present invention the absorbent core may provide the wearer facing surface of the article such that this surface of the core also provides the functions of the topsheet.
The breathable backsheet is located on the garment facing surface of the absorbent core and comprises at least a first backsheet layer. It can further comprise additional layers such as a second backsheet layer. The first backsheet layer is positioned between the garment facing surface of the absorbent core. In order to provide the article with breathability all backsheet layers are at least water vapor permeable, preferably air permeable. The first backsheet layer comprises a resilient three dimensional web, which consists of a liquid impervious polymeric film which film has apertures. The apertures form capillaries which have side walls which extend away from the wearer facing surface of the film providing the web with three dimensionality. The capillaries have a first opening in the garment facing surface of the film and a second opening at the end of the capillaries spaced apart from the wearer facing surface of the film. Preferably the capillaries extend away from the wearer facing surface of the film at an angle which is less than 90xc2x0 in respect to the plane of the film.
In co-pending patent applications based on priority document EP 98101867 and EP 98101868 a combination between a slanted capillary film backsheet, an optional second of the film. The center axis is defined as the line which connects the center point of the first opening of a capillary and the center point of the second opening of a capillary.
For some embodiments it is also possible that the first opening of at least some of the capillaries is larger than the second opening of the respective capillary such that the capillaries themselves form cones which have an increase in capillary action in a direction towards the absorbent core. In yet another embodiment according to the present invention the capillaries are curved towards or appear bent towards the plane of the film. In an alternative or in addition thereto the capillaries have a first and a second portion which are different in direction, form, shape, size or combinations thereof.